Fuel fired furnace



Aug. 2, 1932. w. A. DARRAH FUEL FIRED FURNACE Filled June 25, 1927 Figure .3.

Patented Aug. 2, 1932 ...mwen-...m

WILLIAM A. DARRAH, OF CHICAGO, ILLINOIS FUEL einen FURNACE Application. filed June 25, 1927. Serial No. 201,480.

This invention relates to equipment for hea-ting materials by fuel and is particularly applicable Vto furnaces fired with gas, oil or powdered coal.

The object of this invention is to provide a simple, eficient, economical equipment for heating to high commercial temperatures with a minimum amount of oxidation of the material being heated. Another object of this invention is to provide equipment which will transmit heat to the materials being heated in a relatively short time. Another object of this invention is to provide heating equipment such that the materials being heated will receive their heatinain'ly from radiation and only in a small way from convection.

This equipment is particularly applicable to the melting of metals such as iron, alloys7 brass, aluminum, etc., but the principles disclosed herein may be applied to other Voperations, such as forging, heat treating, annealing, roasting, etc. 'It should be understood that this equipment is not limited to any 5 specific temperature or materials. i

Referring to the drawing:

Fig. I shows a side elevation partly in section of one form of my device.

The section shown in Figure I is taken 3o along the line indicated in 1-1 in Figure II.

Fig. II shows a front elevation partly in section, the section shown is taken along section line 2-2 of Figure I;

Fig. III shows a plan view also partly in section; the section shown is taken along the line SA-BA.

Fig. IV shows a section taken through the recuperator; the section shown is taken along line 4-4 of Figure I. f

The form of my invention embodied on the drawing, comprises a furnace shell (1) equipped with a door (2) and mounted in a trunnion or bearing (3) in such a manner as to be able to oscillate either for discharging, 5 charging or while heat is being applied.

A cylinder which may be operated either by air, water or other convenient means serves to tilt the furnace in the desired manner. Air for combustion purposes is introw duced in the furnace'l7 Pipelf) and' fuel such as gas, oil or powdered material by pipe (6). Cylinder (4) is connected to a flange (7) at the rear portion of the furnace by a head (8) on the end of piston rod (9) which;

operates in cylinder (4).

Fralne (l) is lined with refractory insulation as indicated on the sides of the furnace by (10), the bottom of the furnace by (11) and around the vertical shaft of the furnace,

by (12),. TNithin the insulation is placed a refractory lining or support (13) and within the refractory lining or support is a special refractory material (14) which serves as a hearth or container for the materials beingf heated. An arch (15) is thrown over the hearth and insulated by heat resisting insulation (16) and low temperature insulation (17) in the manner shown. The top wall is formed with a series of projecting portions giving a serrated surface for purposes later j tor through the space (21) between the re-l cuperator tube and the wall. The air travels downward in the direction shown by the solid arrows circling the tubes and leaves the lower portion of the recuperator by port (22) which directs it to the burner port (23).

The fuel which for purposes of convenience in this discussion will be assumed to be gas, enters through pipe (6) which may be attached to a iexible tube or hose or joint not shown. The gas travels through a refractory tube (24) placed within the air port (23) and so arranged that the gas leaves the end of the tube (24) and mixes with the heated air in combustion chamber (25). j

The products of combustion travel longitudinally in combustion chamberv (25) toward the front portion of the furnace and then travel upward at the end of combustion chamber (25). rlhis path of travel is maintained by reason of a covering wall (26) which extends over the top of combustion chamber (25) at its rear portion, while an opening (27) is provided at the forward portion.

Combustion chamber (25) is formed between the outward wall of the furnace (28)V and an inner combustion wall (29) which l prefer to make of a refractory material which is a good conductor of heat. Refractory wall (29) may to advantage be constructed from silicon carbide or other high conductive refractory material. l have found it convenient to build wall (29) from carborundum bri-ck and to construct hearth (14) from carborundum cement. Obviously the entire stretch of lining formed by hearth (la) and wall (29) may be made of a refractory brick having the desirable heat conducting properties or both portions may be formed from a refractory cement.

When the gases leave combustion chamber (25) through opening (27) they travel in the direction shown by the arrows of Fig. l and IV backward under the arched roof of the furnace passing throuO'h series of iiues (30, 31, 32, etc.) upward through the refractory recuperator tubes (20) leaving through opening (33) which serves as a vent or stach. The size of opening is adjustable vby means of a damper (24) which restricts the rate or flow of products of combustion from the furnace.

Arched roof (l5) with projecting portions (18) becomes highly heated by the products of combustion as they leave the furnace, thus serving as a source of radiant heat which is, of course, radiated to material located in the hearth of the furnace. The side walls (29) also serve as a source of radiation, thus the back wall (35) which is heated by the products of combustion as they leave the furnace. At the same time, the hearth of the furnace serves as a source of conducted heat by reason of the factthat it is a good conductor in intimate contact with the combustion chamber. A spout or pouring lip (36) may be provided to direct the flow of melted material from the furnace in case the equipment is used as a melting device, also l wish it to be distinctly understood that the principles set forth in this specification may be applied to furnaces for a great variety of purposes and are not confined wholly to melting which, however, is one desirable application and has been chosen for purposes of description as a convenient means of illustrating this invention.

It will be noted thatthe furnace constructed in accordance with my invention provides means fer consuming the fuel lin combustion chambers in such a way that combustion does not take place in contact with the material being heated. On the other hand, thematerial which it is desired to heat receives heat mainly by radiation as for example from the roof and sides of the furnace and also by conduction through the hearth of the furnace.

This construction perm-its a high efficiency in that combustion is complete a properly designed combustion chamber and not retarded or inuenced by the chilling effect of ceel material such as the substance being heated. Products of combustion give up their heat to the surfaces of the furnace as for example the serrated roof thus causing this portion of the furnace to serve as a source of radiation. The serrations which are shown merely diagrammatically, as any desired contour or arrangement may be employed, serve to create eddies thus insuring intimate contact between the heated gases and the radiating surface. The serrations also serve to materially increase the radiating surface and the uniformity of the source of radiations. The serrations also serve in a measure asa heat storage, so that if the furnace is initially heated and a cold charge introduced, it is not always necessary to burn enough fuel during the heating of the cold charge as .in many cases sufficient heat will be obtained from that stored in the furnace.

l also wish to point out that the arrangement by which the recuperator is constructed within the furnace permits the direct application of the heated air into the combustion chamber without involving the use of outside piping, fittings, valves, etc., which always serve as additional source from which heat may be lost or from which the air may leak. rlhis construction also greatly simplifies the furnace.

In the case chosen for illustration l have shown a tilting furnace which is admirably suited for melting purposes. I have used such a furnace for meltingglass, copper. iron, brass, aluminum and similar purposes. y

It will be evident that by making simpl(` constructions, the furnace may be used as a heating` furnace as for example for forging. welding or similar operations. i

VOne of the advantages of this furnace is the very material reduction in scaling or oxid ation. of the materials being heated.V I have found that in the case of melting brass or heating steel a flame directed immediately on the substance being heated causes high losses due to oxidation or scaling. As a theory, which l believe to be correct, it would appear that the high losses which result in this case are due to the fact that certain portions of the surface of the materials being heated are raised to extremely high temperatures very rapidly, while an appreciable time is otherwise required for the heat to penetrate to the interior of the substance being heated.

. rials being melted and is radiated substantially uniformly and at controlled rates over substantially the entire exposed surface. Localized heating is, therefore, avoided and scaling, slagging, or oxidation is reduced.

As distinguished from this factor in my furnace, a. stream of products of combustion gives intense local heating directly in its path and a much slower rate of heating at all points not directly in its path.

It will be apparent that many changes may be made in the structure shown and described without departing f-rom the spirit of this invention and I do not wish to be confined to the exact arrangement disclosed herewith.

In referring to refractory materials Ii intend to designate such substances as firek brick, fire clay, sillimanite, silica, alumina oxide compounds, etc. In referring to heat conducting materials or materials of relatively good heat conductivity, I intend to refer to such substances as silicon carbide, chrome oxide compositions, carbon and other dense homogeneous bodies, having a higher heat conductivity than ordinary fire clay.

Having now fully described my invention what I claim as new and wish to secureby Letters Patent in the United States is as follows:

l. A furnace comprising a housing, means for inclining said housing, a refractory hearth within said furnace, a combustion chamber adjacent said hearth, said combustion chamber having a heat conducting refractory wall adjacent said hearth, and a roughened roof over said hearth, arrangedto be heated by products of combustion from said combustion chamber.

2. A furnace consisting of a housing, a combustion chamber within said housing, a heating chamber within said housing, a kheat conducting refractory wall separating said heating chamber and said combustion chamber, means for introducing fuel at one end of said combustion chamber, the products of combustion passing through an opening formed near one end of said combustion chamber into said heating chamber and an exhaust port near the end of said heating chamber opposite said opening.

3. In a furnace a heating chamber arranged to be heated primarily by radiation, a combustion chamber separated from said heating chamber by highly heat conducting 4. In a furnace a heating chamber, a hearth of heat conducting refractory material in said heating chamber, a combustion chamber adjacent said heating chamber and in contact with said hearth, said combustion chamber being located at one side of said hea-ting chamber, and a cover over a portion of said combustion chamber, and an outlet being formed near the top portion of said combustion chamber communicating with the space above said hearth in said heating chamber.

5. A fuel fired furnace consisting of a refractory hearth, a heating chamber, a combustion chamber, said combustion chamber being arranged adjacent to and beside said heating chamber, a heat conducting refractory wall separating said combustion cha1nber from said heating chamber, a cover over a portion of the top of said combustion chamber, an outlet near the top of said combustion chamber communicating with the space above said hearth and within said heating chamber, and a container for enclosing said hearth and said combustion chamber;

6. In a furnace, a housing, a heating chamber within said housing, a combustion chamber adj acent and beside said heating chamber and within said housing, a refractory wall separating said heating chamber and said combustion chamber, means for introducing the fuel at one end of said combustion chamber, the products of combustion passing through an opening formed near one end of said combustion chamber into said heating chamber and an exhaust port near the end of said heating chamber opposite saidV opening.

WILLIAM A. DARRAI-I.

walls, a heat conducting hearth in said heat'- 

